1. Field
This disclosure relates generally to filters for electromagnetic signals and, more specifically, to tunable filters for use with radio frequency, microwave frequency, or millimeter wave frequency signals.
2. Description of Related Art
Filtering devices for filtering radio frequency, microwave frequency, and millimeter wave frequency signals are well known in the art. Stripline or planar microstrip filters are examples of filters used in microwave systems. These filters have the advantage of being relatively small, but they also have a relatively high insertion loss and are typically not easily tunable.
Combline filters or Capacitively Loaded Interdigital Filters (CLIF) are also known in the art. These filters usually have a lower insertion loss than the stripline or planar microstrip filters, but combline filters or CLIFs are typically larger in size than the stripline or planar microstrip filters. Combline filters or CLIFs may not be tunable. Those combline filters or CLIFs that are tunable typically exhibit a response time on the order of milliseconds, due to the relatively large size of such filters. Also, the relatively large size of such filters typically requires fabrication using machine shop processing techniques, rather than wafer scale processing that is typically used for smaller electronic components.